The present application relates generally to an improved data processing apparatus and method and more specifically to a wafer-level chip-scale package utilizing conductive polymer.
Wafer-level chip-scale package (CSP) (WLCSP) refers to a technology of packaging an integrated circuit at a wafer level, resulting in a device practically the same size as the die. WLCSP provides a solder interconnection directly between a device and an end product's motherboard. WLCSP includes wafer bumping (with or without pad layer redistribution or redistribution layer (RDL)), wafer level final test, device singulation, and packing in tape and reel. Some of the most widely offered WLCSP options include WLCSP bump on pad (BOP) and WLCSP with a redistribution layer (RDL).
The WLCSP bump on pad (BOP) option provides a reliable, cost-effective, true chip-size package on devices not requiring redistribution. The WLCSP BOP option utilizes a repassivation polymer layer with excellent electrical/mechanical properties. Under-Bump-Metallurgy (UBM) is added and solder bumps are then placed directly over die I/O pads. WLCSP-BOP is designed to utilize industry-standard surface mount assembly and reflow techniques.
The WLCSP with a redistribution layer (RDL) option adds a plated copper Redistribution Layer (RDL) to route I/O pads to Joint Electron Device Engineering Council (JEDEC)/Electronic Industries Association of Japan (EIAJ) (JEDEC/EIAJ) standard pitches, avoiding the need to redesign legacy parts for CSP applications. A nickel based or thick copper UBM, along with polyimide or polybenzoxazole (PBO) dielectrics, provide improved board level reliability performance. WLCSP with RDL utilizes industry-standard surface mount assembly and reflow techniques, and does not require underfill on qualified device size and I/O layouts.
Therefore, WLCSP has seen tremendous growth as a true chip scale package, by allowing direct chip attach of a flip chip die without underfill, but is restricted to relatively small die size and low I/O count. WLCSP has seen tremendous growth for mobile and smart phone application, especially for power management ICs.